Continuous duty press monitoring system

ABSTRACT

A continuous duty press monitoring system includes a linear variable displacement transducer mounted to a press frame as to acquire data related to stresses and strains in the press housing due to completion of a press operation. First and second oppose, spaced apart ends of a rod member are secured to the press housing or frame. The first send is secured to so as to cause axial movement of the rod in accordance with the frame movement at that point. The second portion is secured to the housing so as to allow the second end to be slidable in relation thereto. A linear variable displacement transducer is secured at the slidably affixed end of the rod. A magnetic flux generated by application of current to a coil of the transducer is affected by relative positioning of the rod thereto. Press operation thereby provides an indication, due to stresses or strains resultant on the press housing, as to the characteristics of a particular press operation. Flux variations provide an analog signal representative of these press characteristics. This analog signal is communicated to a continuous plotter, a digitized version of which is further communicated to a microprocessor controller. An alarm is advantageously generated when preselected characteristics have been exceeded by press operation.

This application is a Reissue of Ser. No. 08/019,017 filed Feb. 18, 1993now U.S. Pat. No. 5,440,499. .Iaddend.

BACKGROUND OF THE INVENTION

This application pertains to the art of press fabrication and moreparticularly to control of a pressing operation or run. The invention isparticularly applicable to continuous, real-time monitoring of pressoperation and will be described with particular reference thereto.However, it will be appreciated that the invention has broaderapplications such as in any system in which stress or straincharacteristics are advantageously measured or monitored continuously,accurately, and in real time.

A substantial number of manufactures are formed through punching orpress operations. In such an operation, raw material, such as steel orother malleable metal is subjected to a high-force blow from a die.Application of insufficient force will result in underformed ormalformed workpieces. Excessive force may damage the workpiece or thepress itself. Further, excessive force may be indicative that the pressis being operated at too high a level. That is, the particular pressoperation may be more suitable for a press of higher capacity or force.

Some earlier systems have attempted to address these concerns byutilization of press housing strain characteristics to determine forceof a particular press blow. A mechanical strain gauge was affixed to apress housing. The strain gauge would be manually reset and a readingobtained after a single blow of a press operation. The strain gaugereading obtained from this blow would be utilized to determine whetherthe press was utilized beyond capacity during setup of a run. Typically,several sample workpieces would be so measured, with a manual reset ofthe strain gauge between each workpiece.

These systems provide useful information during the set up operation ofa particular workpiece run. However, the mechanical nature of the straingauge is utilized and the manual reset requirements limited its utilityto such set ups.

The present invention contemplates a new and improved press monitorwhich provides not only intermittent or set-up press characteristics,that provides continuous, real-time and non-supervised monitoring andcontrol of a press operation.

SUMMARY OF THE INVENTION

In accordance with the subject invention, there is provided a linearvariable displacement transducer which includes a coil portion movablyconnected to a core portion such that the magnetic flux generated bycurrent impressed on the coil is influenced by a position of the corerelative thereto. A securing means is provided for securing the coreportion and the coil portion to spaced apart portions of a housing of anassociated press. This is accomplished such that compression andexpansion of the housing will influence a relative position of the coreto the coil. An alternating current is impressed on the coil andvariations in the resultant magnetic flux, due to the relative positionof the core, is monitored. A signal is generated representative of thisrelative position.

In accordance with a more limited aspect of the present invention, thesignal is digitized and filtered to provide a press deflection systemwhich bears information on the force being imparted to a workpiece inthe press.

In accordance with a more limited aspect of the present invention, ameans is provided for archiving or generating a printout of presscharacteristics.

In accordance with another aspect of the present invention, a method forcompleting a series of press operations with continuous characteristicmonitoring with the above structure is provided.

In accordance with yet another aspect of the present invention, a systemis provided for automatically zeroing the same to achieve a consistentminimum output when a press is unloaded.

An advantage of the present invention is the provision of a pressmonitoring system adapted for continuous, uninterrupted and unsupervisedduty.

Another advantage of the present invention is the provision of a systemwhich allows for building a record of press characteristics associatedwith each workpiece fabricated therefrom.

Yet another advantage of the present invention is the provision of asystem by which compressed characteristics may be compared topreselected standards to determine acceptability thereof.

Further advantages will become apparent to one of ordinary skill in theart upon a reading and understanding of the subject specification.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take physical form in certain parts and arrangementsof parts, a preferred embodiment of which will be described in detail inthis specification and illustrated in the accompanying drawings whichform a part hereof and wherein:

FIG. 1 illustrates a press machine and monitor/controller in accordancewith the present invention;

FIGS. 2A and 2B illustrate a top and side view of the transducer arrayas utilized in connection with the monitor of FIG. 1;

FIG. 3 illustrates a block diagram of the data acquisition/control unitas illustrated in FIG. 1;

FIG. 4 provides a flow chart of the logical flow in connection with apress monitor/control system of FIGS. 1-3;

FIG. 5 provides a flow chart of an automatic zeroing function of thesubject monitor/control system.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Turning now to the illustrations wherein the showings are for thepurpose of illustrating the preferred embodiment only, and not for thepurpose of limiting the same, FIG. 1 illustrates a press A, a linearvariable displacer transducer ("LVDT") mechanism B, and a dataacquisition/controller unit C.

The press A is suitably comprised of any, conventional press mechanism.Such a mechanism includes a ram 10 disposed adjacent to a platen 12. Aswill be understood, typical workpiece formation, such as in a formationof a workpiece 14, is accomplished by provision of a die or tooling inat least one of ram 10 and platen 12. The press A is illustrated as amotor-driven system employing a motor/gear arrangement 16 to drive theram 10. However, it will be appreciated that any ram, such as ahydraulically driven ram, may suitably be utilized in connection withthe subject system.

The ram A includes a frame or housing portion 20 which links the ram 10with the platen 12. It will be appreciated that operation of the pressresults in an induced stress or strain on the frame 20.

The LVDT mechanism B is secured to the frame 20 in a fashion to bedetailed below. Stresses and strains within the frame 20, induced byoperation of the press A, are measured by the mechanism B. These signalsare, in turn, communicated to the data acquisition/controller unit Cwhich will also be detailed below.

Also illustrated is a second LVDT B' which is shown as encased in ametallic housing 22. Such a second LVDT may be utilized forcomplimentary data acquisition or redundancy, and is interfaced toeither the data acquisition/controller C, or to a secondary, similarunit C' (not shown). The LVDT B is, in the preferred embodiment, alsoencased in housing to similarly isolate it from debris and particulatematter, although it is not shown for illustrative purposes.

FIGS. 2A and 2B illustrate, in detail, a preferred fabrication of theLVDT mechanism B. FIG. 2A illustrated a top view while FIG. 2Billustrates a side view. In the LVDT mechanism, a rod member 26 includesopposed, first and second spaced-apart ends 28 and 30. The elongated rod26 is suitably formed of a relatively inflexible material, such ashardened steel. First end 28 is secured to the frame 20 (FIG. 1) with afastener such as illustrated by bolt 34. The fastener or bolt 34functions to secure the first end to the frame so as to allow axialdisplacement of the rod 26 corresponding to frame movement at a firstmounting point, defined as that accomplished with fastener 34.

The second end 30 is slidably received into a support member 36 whichallows axial movement of the rod 26 with respect thereto. The supportmember 36 is, in turn, originally secured to a base plate 38 viafasteners 42. Similarly, the base plate 38 is affixed to the frame 20(FIG. 1) via fasteners 44 and further secured by a dowel pin 45.

The system advantageously employs an intermediate support member 46disposed between the first and second space apart ends 28, 30. Supportmember 46 is second to the frame 20 with fasteners 48. Like the supportmember 36, the member 46 allows axial movement of the rod 26 withrespect thereto.

With the afore-described arrangement, it will be appreciated thatstresses and strains of the frame are measured by a relative position ofsecond end 30 relative to each portion of the base plate 38. While suchstresses and strains are relatively small, they are exaggeratedproportionally to the distance between ends 28 and 30 which isdetermined by the length of the rod 26. A bolt mechanism 50 is securedcoaxially to the rod 26 at an extreme of second spaced apart ends 30.This bolt is, in turn, connected to a movable portion of a linearvariable displacement transducer 52. A suitable LVDT is manufactured byLucas Schaevitz of Pennsauken, N.J. The LVDT 52 employs a coilmechanism, movable relative to a core mechanism. Accordingly, magneticflux induced in the coil is affected by the relative position of thecore thereto. With this arrangement, the LVDT 52 which is secured to thebase plate 38 by fasteners 54, is adapted for generating a signalrelative to longitudinal stresses and strains on the frame 20.

Turning now to FIG. 3, a detailed description of the dataacquisition/controller unit C is provided. It will be noted that theLVDT 52 includes a core 60 which is coaxially secured to the rod 26(FIGS. 2A and 2B). An oscillator/driver 62 imparts a current to a coil64, thereby inducing a magnetic flux therefrom. The core 60 is ferrousand disposed physically approximate to the coil 64. Accordingly, fluxgenerated by application of current form the oscillator/driver 62 isaffected by relative position of the core 60 thereto. A sensor coil 68of the LVDT 52 acquires information as to properties of the flux, andprovide a signal from voltages induced therefrom to a demodulator 70.

At this point, an analog signal from demodulator 70 is communicated to afilter 72. The signal is them communicated to a buffer/amplifier 74 anda programmable gain amplifier 76 through a summer pair to be describedfurther below. The signal to the buffer/amplifier 74 is communicated toa continuous analog recorder output, such as a plotter at port 80. Thesignal from amplifier 76, which is an amplification from that of filter72, is provided to a peaks detector 78.

A first switch 86 is closed to provide an output from peak detector 78to an analog to digital (A/D) converter 88. The A/D converter 88 servesto digitize this signal for communication to a microprocessor basecontroller 90. The switch 86 is opened and a switch 92 is closed toshort out the peak detector 78. Accordingly, the switch 92 allows forzeroing of the system to stable conditions. The digitized signal fromA/D converter 88 is provided to the controller 90, operating undersoftware as detailed below. The controller 90 also includes an alarmoutput 94, a port for bi-directional serial link 96, an end of cyclesignal receiving port 98. Common controllers also include means 100 forreceiving data from additional channels such as from a second LVDT, aswell as means for communicating data to such additional channels. Thesystem also employs a key pad for manual data entry, as well as adisplay as illustrated by LCD readout area 106. An external display 110has also advantageously employed to provide an indication as tomonitored press characteristics outside of the actual controller area.

A signal from controller 90 is communicated to a digital to analog("D/A") converter 114 to a summer 116. The summer 116 sums the signalreceived from filter 72 to form a composite signal therewith. With thisarrangement, it will be appreciated that a feedback loop is provided forenhancing stability and accuracy of the system as determined by thecontroller 90. Further, a bias voltage, generated from bias generator120 is selectively applicable, via a switch 122 to a summer 120. Thisbias allows for additional controller and stabilizing of the signal fromthe filter 72 and for the purpose of maintaining an optimized signalrange to peal detector 78. However, bias is not communicated directly toinfluence the buffer amplifier and, accordingly, the printout achievedfrom port 80.

Turning now to FIG. 4, a flow chart of the instructions of thecontroller 90 is illustrated. The procedure for continuous monitoring iscommenced at block 130. From this point, progress is made to block 132which represents retrieval of data representative of a selectedthreshold. This data is advantageously user definable via user inputfrom serial link port 96 or keypad 110.

Next, progress is made to block 134, at which point strain gauge data,obtained in accordance with an output of the LVDT 52 (FIG. 3). isachieved. At block 136, the strain gauge data is communicated to arecorder 138 which may be suitably formed of any non-volatile datastorage mechanism such as a static memory.

Strain gauge data is then compared to first and second threshold data atblock 140. At block 142, a determination is made as to whether the firstthreshold value is exceeded. A positive determination enables a warninglight at block 144. At this point, or upon a negative determination atblock 142, progress is made to block 146.

Next, a determination is made as to whether a second threshold value isexceeded at block 146. A positive determination results in the soundingof an alarm at block 148 by application of a signal from microprocessorbased controller 90, via alarm output 94 (FIG. 3). This causes progressto block 150, at which state the system remains pending operation entryof a preselected code into keybed 110. Entry of such a code causesprogress to block 152.

A negative determination in block 146 facilitates determination as towhether an end of cycle signal is present, as received from port 98(FIG. 3). A positive determination from the end of cycle signal at block152 directs an end of procedure at block 154. A negative determinationat block 152 directs the system to proceed back to block 134, at whichpoint additional strain gauge data is obtained from the current presscycle.

With the above-described structure, it will be appreciated that a meansby which continuous, reliable press operation data is acquired andtested during a press operation. Undesirable press characteristics orflawed pieces may be determined throughout a production run. Such acontingency may result in the termination of a production procedure.Further, a historic record is provided on a procedure for closed-loopsystem monitoring and quality control. This data is obtainable via thebi-directional general serial link at 92 (FIG. 3).

Referring now to FIG. 5, a procedural flow chart detailing operation ofan automatic zeroing subsystem is illustrated. This function, referredto as "auto-zeroing" is executed when the monitor device, such as thepress, is idle. If the device commences a load cycle, the function isimmediately aborted without adjustment so that load cycle data integritymay be maintained

The auto-zero procedure is commenced at block 200. Proceeding next toblock 202, a determination is made as to whether the press had been idlefor a preset duration. This preset duration is chosen to allow forsettling of the structure. A negative determination at block 202 causesa "wait loop" by repeating the test. A positive result at block 202causes progress to block 204, at which point analog circuitry is setup.The peak detector 78 and bias generator 120 are disabled and theprogrammable gain amplifier 76 is reconfigured at this point.

Next, at block 206, acquired data is compared to fixed (non-alterable)data. A determination is then made at to whether the mean value thereofis within preselected operational limits. A negative determinationsignifies an error condition which triggers an alarm at block 210 and anunconditional abort of the process at block 212. The alarm at block 210includes the displaying of a message, on a liquid crystal display in thepreferred embodiment, disclosing a nature of the malfunction to anoperator. No further data is acquired from this channel in subsequentload cycles as it would be invalid.

A positive determination at block 208 causes progress to block 214. Atthis point, a digital value is calculated which will negate the dataobtained in block 206. This value is then normalized and sent to thedigital analog converter 114 in block 216.

From block 216, progress is made to block 218, at which point all analogcircuitry for bias, gain, and peak detection are returned to theirnormal operating states. Control is then returned to the main monitoringroutine outlined in FIG. 4, above at end procedure block 212.

The invention has been described with reference to the preferredembodiment. Obviously, modifications and alterations will occur toothers upon the reading and understanding of this specification. It isintended that all such modifications and alterations be included insofaras they come within the scope of the appended claims or the equivalentsthereof.

Having thus described the invention, it is now claimed:
 1. A pressoperation data acquisition apparatus comprising:a linear variabledisplacement transducer including a coil portion movably disposedrelative to a core portion such that magnetic flux generated by currentimpressed on the coil portion is influenced by a position of the coreportion relative thereto; securing means adapted for securing the coreportion to a first portion of a housing of an associated press and thecoil portion to spaced apart portions of the housing of the associatedpress such that compression and expansion of the housing will influencea relative position of the core portion to the coil portion; means forproviding an electric current to the coil portion; means continuouslysensing the magnetic flux induced by operation of the associated pressby monitoring of current in the coil portion; position signal generatingmeans for periodically generating a position signal representative of arelative position of the coil portion to the core portion in accordancewith sensed magnetic flux; and calibrating means adapted forautomatically calibrating the position signal to a base level prior tocompleting a press cycle of the associated press; means for generating apress deflection signal in accordance with the position signal.
 2. Thepress operation data acquisition device of claim 1 further comprisingmeans for generating a display signal in accordance with the pressdeflection signal.
 3. The press operation data acquisition device ofclaim 2 further comprising means for recording the press deflectionsignal.
 4. The press operation data acquisition device of claim 3wherein the means for recording the press deflection signal is comprisedof at least one of a plotter, a printer and a data storage unit.
 5. Thepress operation data acquisition device of claim 1 wherein the positionsignal generating means includes:means for acquiring an analog signalrepresentative of sense magnetic flux; means for digitizing the analogsignal; and means for filtering the digitized analog signal to form theposition signal as digitized position signal.
 6. The press operationdata acquisition device of claim 5 further comprising:comparator meansfor comparing the digitized analog signal to a comparison thresholdvalue; and means for generating an alarm signal when the digitizedanalog signal exceeds the comparison threshold value.
 7. The pressoperation data acquisition device of claim 6 further comprising:meansfor acquiring data representative of a selected threshold value; meansfor communicating the selected threshold value to the comparator meansas the comparison threshold value.
 8. The press operation dataacquisition device of claim 7 further comprising means adapted fordisabling an associated press in accordance with the alarm signal. 9.The press operation data acquisition device of claim 7 furthercomprising a container means for monitoring a minimum output from themonitored press during unloading thereof.
 10. A press operationmonitoring method comprising the steps of:activating a press to performa stamping operation; monitoring deformation of a frame of the pressrelative to opposed first and second, spaced apart ends of a rod member,the first spaced apart end being mounted to the frame at a firstmounting point so as to allow axial displacement of the rodcorresponding to frame movement at the first mounting point, and thesecond spaced apart end being mounted to the frame at a second mountingpoint such that the rod axis is slidable relative to the second mountingpoint; generating, via a linear variable displacement transducer securedto the second spaced apart end, a press deflection signal representativeof the deformation induced by operation of the press; automaticallycalibrating the press deflection signal to a base level prior to thestep of activating; and generating a display signal in accordance withthe press deflection signal.
 11. The method of claim 10 furthercomprising the step of generating a tangible, historic record of theframe deformation in accordance with the press deflection signal. 12.The method of claim 11 further comprising the steps of:comparing thepress deflection signal to a comparison threshold value; and selectivelygenerating an alarm signal in accordance with a result of the step ofcomparing.
 13. The method of claim 12 further comprising the stepsof:digitizing the press deflection signal to form a digitized deflectionsignal; filtering the digitized deflection signal to form a filtereddigitized analog signal; and wherein the step of comparing includes thestep of comparing the filtered digitized analog signal to the comparisonthreshold value formed as a digitized value.
 14. A press operation dataacquisition device comprising:securing means adapted for securing aframe of the press relative to opposed first and second, spaced apartends of a rod member, the first spaced apart end being mounted to theframe at a first mounting point so as to allow axial displacement of therod corresponding to frame movement at the first mounting point, and thesecond spaced apart end being mounted to the frame at a second mountingpoint such that the rod axis is slidable relative to the second mountingpoint; a linear variable displacement transducer including a coilportion secured to the frame at the second mounting, and a core portionsecured to the rod at the second spaced part end such that a magneticflux generated by application of current to the coil portion is affectedby a relative position of the core portion thereto; means for providingan electric current to the coil portion; sensing means continuouslysensing the magnetic flux during operation of the associated press bymonitoring of current in the coil portion; means for acquiring an analogflux level signal representative of sensed magnetic flux from thesensing means; digitizing means for digitizing the flux level signal toform a digitized flux level signal; filter means for filtering thedigitized flux level signal to form a position signal; calibrating meansadapted for automatically calibrating the position signal to a baselevel prior to completing a press cycle of the associated press; andmeans for calculating a press deflection signal representative of arelative position of the coil portion to the core portion in accordancewith the position signal.
 15. The press operation data acquisitiondevice of claim 14 further comprising means for generating an outputsignal representative of the press deflection signal.
 16. The pressoperation data acquisition device of claim 15 further comprising:meansfor storing a digital threshold value representative of at least one ofan upper threshold level and a lower threshold level; comparator meansfor comparing the press deflection signal to the digital thresholdvalue; and means for generating a comparison signal in accordance with acomparison in the comparator means.
 17. The press operation dataacquisition device of claim 16 further comprising means for selectivelygenerating an alarm signal when the comparison signal indicates that thepress deflection signal surpasses the threshold level.
 18. The pressoperation data acquisition device of claim 17 further comprisingarchiving means for archiving the output signal.
 19. The press operationdata acquisition device of claim 15 wherein the archiving means includesa plotter.
 20. The press operation data acquisition device of claim 19wherein the archiving means includes a non-volatile digital memory..Iadd.
 21. A data acquisition apparatus for a metal forming machine,comprising:a linear variable displacement transducer including a coilportion movably disposed relative to a core portion such that magneticflux generated by current impressed on the coil portion is influenced bya position of the core portion relative thereto; securing means adaptedfor securing the core portion to a first portion of a housing of anassociated metal forming machine and the coil portion to spaced apartportions of the housing of the associated metal forming machine suchthat compression and expansion of the housing will influence a relativeposition of the core portion to the coil portion; means for providing anelectric current to the coil portion; means continuously sensing themagnetic flux induced by operation of the associated metal formingmachine by monitoring of current in the coil portion; position signalgenerating means for periodically generating a position signalrepresentative of a relative position of the coil portion to the coreportion in accordance with sensed magnetic flux; and calibrating meansadapted for automatically calibrating the position signal to a baselevel prior to completing a cycle of the associated metal formingmachine; means for generating a deflection signal in accordance with theposition signal. .Iaddend..Iadd.
 22. The data acquisition device ofclaim 21 further comprising means for generating a display signal inaccordance with the deflection signal. .Iaddend..Iadd.23. The dataacquisition device of claim 22 further comprising means for recordingthe deflection signal. .Iaddend..Iadd.24. The data acquisition device ofclaim 23 wherein the means for recording the deflection signal iscomprised of at least one of a plotter, a printer and a data storageunit. .Iaddend..Iadd.25. The data acquisition device of claim 21 whereinthe position signal generating means includes:means for acquiring ananalog signal representative of sensed magnetic flux; means fordigitizing the analog signal; and means for filtering the digitizedanalog signal to form the position signal as digitized position signal..Iaddend..Iadd.26. The data acquisition device of claim 25 furthercomprising: comparator means for comparing the digitized analog signalto a comparison threshold value; and means for generating an alarmsignal when the digitized analog signal exceeds the comparison thresholdvalue. .Iaddend..Iadd.27. The data acquisition device of claim 26further comprising: means for acquiring data representative of aselected threshold value; means for communicating the selected thresholdvalue to the comparator means as the comparison threshold value..Iaddend..Iadd.28. The data acquisition device of claim 27 furthercomprising means adapted for disabling an associated metal formingmachine in accordance with the alarm signal. .Iaddend..Iadd.29. The dataacquisition device of claim 27 further comprising a container means formonitoring a minimum output from the monitored metal forming machineduring unloading thereof. .Iaddend..Iadd.30. A monitoring method for ametal forming machine comprising the steps of:activating a metal formingmachine to perform a metal forming operation; monitoring deformation ofa frame of the metal forming machine relative to opposed first andsecond spaced apart ends of a rod member, the first spaced apart endbeing mounted to the frame at a first mounting point so as to allowaxial displacement of the rod corresponding to frame movement at thefirst mounting point, and the second spaced apart end being mounted tothe frame at a second mounting point such that the rod axis is slidablerelative to the second mounting point; generating, via a linear variabledisplacement transducer secured to the second spaced apart end, adeflection signal representative of the deformation induced by operationof the metal forming machine; automatically calibrating the deflectionsignal to a base level prior to the step of activating; and generating adisplay sign in accordance with the deflection signal..Iaddend..Iadd.31. The method of claim 30 further comprising the step ofgenerating a tangible, historic record of the frame deformation inaccordance with the deflection signal. .Iaddend..Iadd.32. The method ofclaim 31 further comprising the steps of:comparing the deflection signalto a comparison threshold value; and selectively generating an alarmsignal in accordance with a result of the step of comparing..Iaddend..Iadd.33. The method of claim 32 further comprising the stepsof: digitizing the deflection signal to form a digitized deflectionsignal; filtering the digitized deflection signal to form a filtereddigitized analog signal; and wherein the step of comparing includes thestep of comparing the filtered digitized analog signal to the comparisonthreshold value formed as a digitized value. .Iaddend..Iadd.34. A dataacquisition device for a metal forming machine comprising: securingmeans adapted for securing a frame of the metal forming machine relativeto opposed first and second, spaced apart ends of a rod member, thefirst spaced apart end being mounted to the frame at a first mountingpoint so as to allow axial displacement of the rod corresponding toframe movement at the first mounting point, and the second spaced apartend being mounted to the frame at a second mounting point such that therod axis is slidable relative to the second mounting point; a linearvariable displacement transducer includinga coil portion secured to theframe at the second mounting, and a core portion secured to the rod atthe second spaced part end such that a magnetic flux generated byapplication of current to the coil portion is affected by a relativeposition of the core portion thereto; means for providing an electriccurrent to the coil portion; sensing means continuously sensing themagnetic flux during operation of the associated metal forming machineby monitoring of current in the coil portion; means for acquiring ananalog flux level signal representative of sensed magnetic flux from thesensing means; digitizing means for digitizing the flux level signal toform a digitized flux level signal; filter means for filtering thedigitized flux level signal to form a position signal; calibrating meansadapted for automatically calibrating the position signal to a baselevel prior to completing a cycle of the associated metal formingmachine; and means for calculating a deflection signal representative ofa relative position of the coil position of the coil portion to the coreportion in accordance with the position signal. .Iaddend..Iadd.35. Thedata acquisition device of claim 34 further comprising means forgenerating an output signal representative of the deflection signal..Iaddend..Iadd.36. The data acquisition device of claim 35 furthercomprising:means for storing a digital threshold value representative ofat least one of an upper threshold level and a lower threshold level;comparator means for comparing the deflection signal to the digitalthreshold value; and means for generating a comparison signal inaccordance with a comparison in the comparator means. .Iaddend..Iadd.37.The data acquisition device of claim 36 further comprising means forselectively generating an alarm signal when the comparison signalindicates that the deflection signal surpasses the threshold level..Iaddend..Iadd.38. The data acquisition device of claim 37 furthercomprising archiving means for archiving the output signal..Iaddend..Iadd.39. The data acquisition device of claim 35 wherein thearchiving means includes a plotter. .Iaddend..Iadd.40. The dataacquisition device of claim 39 wherein the archiving means includes anon-volatile digital memory. .Iaddend.